A straddle carrier is a vehicle for use in e.g. port terminals and intermodal yards used for stacking and moving intermodal containers. Straddle carriers pick up and carry containers while straddling their load and, depending upon capacity, they have the ability to stack containers up to four high. They are capable of relatively low speeds (typically up to 30 km/h) with a laden container, and are generally not road-going.
Conventionally, straddle carriers are equipped with four ground wheels. When the carrier is not used on a level surface, a suspension system is required to ensure the four wheels stay in contact with the ground at all times. However, due to cost, the majority of straddle carriers have no suspension system. Without a suspension system a wheel may lose contact with the ground, therefore losing traction and braking and reducing stability.